Loss of Alkalization in an Alkaline Treated Stator Cooling Water System

摘要

Alkaline treatment of stator cooling water (SCW) systems with copper hollow conductors performs best when pH and dissolved oxygen are kept constant. In the event of loss of alkalization, pH will return to neutral and this will destabilize existing copper oxide layers. Operating experience, however, indicates that infrequent and short-term loss of alkalization does not result in a detrimental buildup of copper oxides in the stator hollow conductors. Thus there is the question as to how long and how often a loss of alkalization can be tolerated. Although operating experience suggests that loss of alkalization can be tolerated for short periods, it is not recommended to allow this routinely and, to the extent practical, SCW pH should be kept constant. Although there is no hard data to support this, an international expert consensus has been found that loss of alkalization of up to one week, and not more than two occurrences per year, can be tolerated. Upon loss, alkalization should be restored to normal as soon as possible. If the loss of alkalization is longer, it is recommended to monitor the water pressure drop across the coils and, if available, also the stator bar temperatures.